1. Field of Invention
The invention relates to a fuel vapor treating apparatus that prevents fuel vapors in a vehicular fuel tank from being discharged to the atmosphere and, more particularly, to a fuel vapor treating apparatus that prevents fuel from being transferred to a canister via a vent line when a fuel tank is filled with fuel and that stops fuel from flowing out when a vehicle inclines or rolls over.
2. Description of Related Art
A vehicular fuel tank is provided with a liquid level sensing valve that closes a vent line when the fuel tank is filled with fuel, a fuel-cut valve that closes an evaporate line to prevent fuel from flowing out of the evaporate line when the vehicle inclines or rolls over, and so on.
Each of these valves is composed of a float that moves vertically in accordance with a liquid level of fuel.
Hereinafter, a known fuel vapor controlling apparatus according to one example of the related art will be described with reference to FIG. 3.
A fuel tank 1 is fitted with a valve casing 4 in which a liquid level sensing valve 2 is integrated with a fuel-cut valve 3.
The valve casing 4 is composed of a lower valve casing 4A and an upper valve casing 4B that is provided above the lower valve casing 4A. A liquid level sensing float 5 and a fuel-cut float 6 are provided in the lower valve casing 4A.
A valve portion 7 is provided on an upper face of the liquid level sensing float 5. A valve portion 8 is provided also in an upper portion of the fuel-cut float 6. Valve ports 9, 10 are provided between the lower valve casing 4A and the upper valve casing 4B. The valve port 9 is opened and closed by the valve portion 7, whereas the valve port 10 is opened and closed by the valve portion 8. The upper valve casing 4B is provided with a vent passage portion 11 that is connected to the valve port 9 via a space portion 12. The space portion 12 is connected to the valve port 10 via a passage 13.
Hereinafter, operation of the known fuel vapor controlling apparatus according to the related art shown in FIG. 3 will be described.
If the pressure of fuel vapors in the fuel tank 1 becomes high during supply of fuel, the fuel vapors pass through the valve port 9 provided in the valve casing 4 and are discharged into a canister (not shown), an intake pipe (not shown) and so on as indicated by an arrow P shown in FIG. 3.
If the liquid level of fuel in the fuel tank 1 becomes high, the liquid level sensing float 5 rises and the valve body 7 closes the valve port 9. Thus, fuel is prevented from being fed directly to the canister and so on.
If the pressure of fuel vapors in the fuel tank 1 remains high during normal operation, the liquid level sensing float 5 is stuck to the valve port 9 and the vent passage portion 11 remains closed. Therefore, the pressure in the fuel tank 1 needs to be reduced.
Thus, the liquid level sensing float 5 is designed to fall because of its own weight.
In the case where the vehicle has greatly inclined or rolled over, there is an apprehension that a large amount of fuel in the fuel tank 1 may flow out toward the canister via the valve port 10 and the passage 13. However, if the vehicle has greatly inclined or rolled over, the fuel-cut float 6 rises and the valve body 8 closes the valve port 10 to prevent fuel from flowing out.
As shown in FIG. 3, while the liquid level sensing float 5 and the fuel-cut float 6 are provided in the same valve casing 4, they are provided in separate valve casings.
A fuel vapor treating apparatus according to a second example of the related art of the invention will be described with reference to FIG. 4.
A fuel tank 21 is fitted with a liquid level sensing valve 22 and a fuel-cut valve 23 separately. A vent passage portion 25 is provided in a valve casing 24 for the liquid level sensing valve 22, and a passage 27 is provided in a valve casing 26 for the fuel-cut valve 23. A space portion 28 is provided in the valve casing 24 for the liquid level sensing valve 22, and a connecting port 29 is provided in the space portion 28. The connecting port 29 is connected to the passage 27 by a hose 30.
Also in the related art shown in FIG. 4, the same operation as in the construction shown in FIG. 3 is performed. Namely, if the liquid level of fuel in the fuel tank 21 becomes high, the liquid level sensing valve 22 closes the vent passage portion 25. Thus, fuel is prevented from being fed directly to the canister and so on.
If the pressure of fuel vapors in the fuel tank 21 remains high during normal operation, the float of the liquid level sensing valve 22 is stuck to the valve port and the vent passage portion 25 remains closed. Therefore, the pressure in the fuel tank 21 needs to be reduced. Thus, using the valve port of the fuel-cut valve 23, the float is designed to fall because of its own weight.
In the case where the vehicle has greatly inclined or rolled over, there is a possibility that a large amount of fuel in the fuel tank 21 may flow out toward the canister via the valve port of the fuel-cut valve 23 and the passage 27. However, if the vehicle has greatly inclined or rolled over, the float of the fuel-cut valve 23 rises to close the valve port and thus prevent fuel from flowing out.
However, the fuel vapor treating apparatuses of the above described related art contain the following problems.
First, since the space portions 12, 28 are directly connected to the vent passage portions 11, 25 respectively, fuel that has leaked from the valve port 9 due to vibration of the vehicle or the like may be transferred toward the canister and adversely affect the canister.
Further, since the valve port 9 is directly exposed to fuel in the fuel tank, fuel may leak from the valve port 9.
Further, in the construction in which the connecting port 29 of the liquid level sensing valve 22 is connected to the passage 27 of the fuel-cut valve 23 by the hose 30 (See, e.g., FIG. 4), assembly of parts cannot be performed by single simple step. Therefore, this operation is time-consuming and laborious and requires preparing a large number of different types of parts. This leads to an increase in number of parts.
Japanese Patent Application No. 11-369719 discloses a fuel vapor treating apparatus that improves the disadvantages of the fuel vapor treating apparatuses of the above related art, including, e.g., reducing an amount of fuel leakage, simplifying the mounting of pipe lines, and reducing the number of parts.
Hereinafter, the fuel vapor treating apparatus disclosed in Japanese Patent Application No. 11-369719 includes the following three features.
First, a partition for stopping the flow of fuel is provided between a space portion of a liquid level sensing valve and a vent passage portion so as to reduce the amount of fuel leakage. Next, a tubular cover covers the liquid level sensing valve so as to prevent a valve port of the liquid level sensing valve from being exposed directly to fuel. Further, a connecting port of the liquid level sensing valve is connected to a passage of a fuel-cut valve by a connector that allows assembly by single simple step, or by a nipple used to make fingertip connection possible, in an attempt to reduce the number of parts and for ease of assembly.
FIGS. 5 and 6 illustrate a third example of the related art. A partition for stopping flow of fuel is provided between a space portion of a liquid level sensing valve and a vent passage portion.
A valve casing of a liquid level sensing valve 41 is composed of a lower valve casing 42 and an upper valve casing 43 that is provided above the lower valve casing 42.
A float 44 is provided in the lower valve casing 42, and a valve portion 45 is provided on an upper face of the float. A valve port 46 is provided between the lower valve casing 42 and the upper valve casing 43 and is opened and closed by the valve portion 45. A vent passage portion 47 is provided in the upper valve casing 43, and a space portion 48 is provided between the vent passage portion 47 and the valve port 46.
In the above construction, the float 44 moves vertically in accordance with a liquid level in a fuel tank (not shown). The valve portion 45 of the float 44 opens and closes the valve port 46, whereby the fuel tank is brought into communication with the vent passage portion 47.
In FIG. 5, a shield member 49, for reducing a cross-sectional area of the space portion 48 is provided in the space portion 48.
Specifically, the shield member 49 has a plurality of shield members 49A and shield members 49B that are alternately disposed. The shield member 49A extends downward from above and the shield member 49B extends upward from below.
Although a fuel-cut valve is not shown in these drawings, the fuel-cut valve may either be integrated with the liquid level sensing valve as shown in FIGS. 3 and 4 or may be separated from the liquid level sensing valve.
According to the above related art, since the shield member 49 stops the flow of fuel, the amount of fuel leakage from the valve port 46 can be reduced.
In addition to the example shown in FIGS. 5 and 6, a fourth exemplary construction that reduces the amount of fuel leakage, by stopping flow of fuel, is shown in FIGS. 7 and 8.
In this example, the space portion between the valve port 46 and the vent passage portion 47 is constructed as a helical passage 48A.
Because other structural components are identical with those of the above example, they are simply denoted by the same reference numerals and will not be described below.
Because the helical passage 48A also stops flow of fuel, the amount of fuel leaking from the valve port 46 can be reduced.
In addition to the above example, a fifth exemplary construction that stops flow of fuel is shown in FIG. 9.
In this example, the space portion between the valve port 46 and the vent passage portion 47 is constructed as a plurality of vertically arranged stepped space portions 48B, 48C and 48D. Vent ports 50 are provided in partitions 49 that separate the space portions from one another. Because the stepped space portions 48B, 48C and 48D also stop flow of fuel, the amount of fuel leaking from the valve port 46 can be reduced.
FIG. 10 illustrates a sixth exemplary construction of the related art that stops flow of fuel. An inflow opening 51 for fuel or fuel vapors is provided in the lower valve casing 42. A tubular cover 52 that covers the inflow opening 51 is either integral with the upper valve casing 43 or provided separately therefrom. By providing a member that covers the inflow opening, fuel can be prevented from reaching the valve port 46 of the liquid level sensing valve 41. Thus, fuel is prevented from being transferred to the canister via the vent passage portion 47.
The various constructions of the above described related art are intended to stop the flow of fuel and to reliably prevent fuel leakage. However, in some cases, fuel may pass through the member designed to stop the flow of fuel and cause leakage.
It is thus an object of the invention to provide a fuel vapor treating apparatus that further reduces an amount of fuel leaking from a fuel tank, that simplifies mounting of pipe lines, and that has a reduced number of parts.
A fuel vapor treating apparatus according to a first aspect of the invention includes a fuel tank that stores fuel, a passage through which vapors of the fuel flow, a space portion interposed between the fuel tank and the passage, a first normally-open valve that closes a first communication passage for communication between the fuel tank and the space portion in accordance with a liquid level of fuel in the fuel tank, and a second normally-open valve that closes a second communication passage for communication between the passage and the space portion in accordance with a liquid level of fuel flowing into the space portion.